HOLOCENE EVOLUTION OF THE CAROLINA CAPES: EVIDENCE FOR A TRANSITION FROM FIVE CAPES TO FOUR

The origin and evolution of the Carolina Capes (Hatteras, Lookout, Fear, and Romain) have been discussed and debated for decades. The formation of these capes has been attributed to Gulf Stream eddies, location of rivers, antecedent geology, and self-organization due to high-wave-angle instabilities in alongshore sediment transport, among other mechanisms. Geologic and morphologic data suggest that a now-abandoned cuspate foreland may have existed on the continental shelf between Cape Hatteras and Cape Lookout. A group of 5-8 lobate, en echelon bedforms, similar to the distal lobes of the modern cape-associated shoals, are present on the mid- and outer-shelf about 20 km offshore of Ocracoke Inlet at 25-33 m water depth. The bedforms are up to 5 m high, spaced several hundred meters apart, and the crests extend along the shelf for 12-20 km. The suggested cape would likely have formed during the early Holocene transgression of the shelf. Available sea-level data suggest that this shelf sector was not flooded until after ~11,000 cal yr BP. Numerical modeling provides insight into the spatial and temporal scale of cape evolution in this setting, suggesting that the high-wave-angle instability in shoreline shape may be responsible for cape formation and evolution, including the subsequent capture of the suggested cape. Seismic, lithologic, and chronologic data from the continental shelf and modern barrier system, coupled with the model results, suggest the cape was probably abandoned in the mid-Holocene when the shoreline likely attained its present four-cape configuration.